This paper presents quality of service (QoS) metrics for continuity and synchronization specifications in continuous media (CM). Proposed metrics specify continuity and synchronization, with tolerable limits on average and bursty defaults from perfect continuity, timing and synchronization constraints. These metrics can be used in a distributed environment for resource allocation. Continuity specification of a CM stream consists of its sequencing, display rate and drift profiles. The sequencing profile of a CM stream consists of tolerable aggregate and consecutive frame miss ratios. Rate profiles specify the average rendition rate and its variation. Given a rate profile, the ideal time unit for frame display is determined as an offset from the beginning of the stream. Drift profile specifies the average and bursty deviation of schedules for frames from such fixed points in time. Synchronization requirements of a collection of CM streams are specified by mixing, rate and synchronization drift profiles. Mixing profiles specify vectors of frames that can be displayed simultaneously. They consist of average and bursty losses of synchronization. Rate profiles consist of average rates and permissible deviations thereof. Synchronization drift profiles specify permissible aggregate and bursty time drifts between schedules of simultaneously displayable frames. It is shown that rate profiles of a collection of synchronized streams is definable in terms of rate profiles of its component streams. It is also shown that mixing and drift profiles of a collection of streams are non-definable in terms of sequencing and drift profiles of its constituents. An important consequence of the mutual independence of synchronization and continuity specification is that, in a general purpose platform with limited resources, synchronized display of CM streams may require QoS tradeoffs. An algorithm that makes such tradeoffs is presented as a proof of applicability of our metrics in a realistic environment.
- Continuous media
- Media mixing